Walruses are definitely a marine animal that makes me think of winter. That's probably because these animals depend on ice to survive - they rest, give birth, nurse, molt and seek protection on sea ice. So walruses are one of those animals that would really be affected by a warming climate.
Aside from climate change issues, there are lots of other interesting things about walruses. Did you know that both males and females have tusks? And unlike some other pinniped species, walrus mothers form relatively long bonds with their young, who may stay with them 2 years or more. Compare that to a harp seal, whose pups stay with their mothers for a mere 12 days!
Image: Walruses resting on an ice floe in the Chukchi sea, courtesy U.S. Geological Survey